Twenty-one minutes after his introduction from the substitutes' bench, Martial bamboozled Martin Skrtel with a mazy run before slotting the ball past Simon Mignolet to score the final goal in United's 3-1 win over their bitter rivals.
"It was a fantastic individual bit of skill, (there was) maybe a bit of luck in there as well, but the way he finished it was incredible and it's a great start from him," United winger Ashley Young said of the £36million teenager.
The fact that the strike came after he had spent just a few days training with his team-mates made the goal more impressive.
The 19-year-old has barely had time to settle into his surroundings
He is living in a city centre hotel and has had to use compatriot Morgan Schneiderlin as a translator because his English is limited to a few words.
"It's early days for him - he's been away on international duty and only trained the last couple of days with us - but he's young and he wants to learn," Young added.
"Morgan is his translator as he doesn't speak much English yet, but if he can go out on the pitch and talk like that, that's enough for us."
Daley Blind, who scored the opening goal from a set-piece drill, was also impressed by the new recruit's debut.
"I'm really happy for him," Blind told MUTV.
"He's a big talent and we all need to be happy that he's in our team and that he created a goal like this."
Van Gaal confirmed on the eve of the match that Michael Carrick and Wayne Rooney had approached him earlier this season to voice their concerns about dressing room morale.
Reports suggested the players had become annoyed at the number of meetings at Carrington, but the constant drills at the training ground meant Blind was in the perfect place to clip home Juan Mata's free-kick four minutes into the second half.
"We practised this goal, and this move, a lot," Blind said.
"Sometimes it went in and sometimes not - normally I have to take a first touch but I struck it at once, which was good."
After going 1-0 down to Blind's curler, Liverpool gifted United a second when Joe Gomez hacked Ander Herrera down in the box and he drove the resultant penalty into the roof of the net.
"Young Joe will learn you have to stay on your feet in the box," was Brendan Rodgers' message to the 18-year-old summer signing from Charlton.
Liverpool's strong start now seems a thing of the past
Rodgers admits things will have to change fast to get the team back on track.
"We need to improve
We are not creating enough chances or building up the game fast enough," he said
"Technically we need to be better in order to keep the ball more."
The only positive for the Liverpool boss was the stunning overhead kick from Christian Benteke which made it 2-1 just moments before Martial killed off the game.
"I thought he was excellent," Rodgers said of the £32.5million forward.
"There aren't too many players who score goals like that."
Source : PA
Source: PA